Stabilized tetraethyl lead antiknock blends



United States Patent Ofiice 3,274,224 Patented Sept. 20, 1966 3,274,224 STABILIZED TETRAETHYL LEAD ANTIKNOCK BLENDS Herman E. Collier, J22, Newark, Del., and John D. Sterling, Jlz, Wenonah, N.J., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed July 25, 1963, Ser. No. 297,687

3 Claims. (Cl. 260437) This invention relates to blends of tetraethyl lead with ethylene dichloride which have been stabilized against thermal decomposition at elevated temperatures.

The desirability of and the problems involved in stabilizing tetraalkyl lead antiknock compounds against decomposition under conditions of thermal stress encountered during various phases of manufacturing, recovery, storage and handling have been discussed in the art, e.g., by Calingaert in US. Patent 2,660,595 and by Cook in US. Patent 3,081,326.

Tetraethyl lead and the other alkyl lead antiknock agents are normally transported, for incorporation into gasolines, as blends comprising essentially the alkyl lead compound and one or more halohydrocarbon scavengers for lead, conventionally ethylene dichloride, ethylene dibromide and mixtures thereof. The ethylene dihalide scavengers together exert a stabilizing effect, and blends of the conventional Motor Mix formulation, consisting essentially of tetraethyl lead, 1.0 theory of ethylene dichloride and 0.5 theory of ethylene dibromide, are regarded as possessing sufficient thermal stability for practical usage. However, it has been found that blends, containing ethylene dichloride as the sole scavenger, i.e., in the absence of the dibromide, are significantly less stable against thermal deterioration at elevated temperatures. Nevertheless, in certain contexts and under certain conditions of motor fuel use, it is highly desirable to employ tetraethyl lead antiknock compositions wherein the scavenger is ethylene dichloride in the absence of ethylene dibromide.

It is an object of this invention to stabilize antiknock blends which consist essentially of tetraethyl lead and ethylene dichloride against thermal decomposition. Another object is to provide blends of tetraethyl lead and ethylene dichloride which are at least as thermally stable as the conventional tetraethyl lead antiknock blends which contain ethylene dibromide. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished according to this invention which comprises an antiknock blend which consists essentially of (A) tetraethyl lead,

(B) about 1 to about 2 theories, based on the lead, of a lead scavenger which consists of ethylene dichloride, and

(C) a small amount, sufiicient to stabilize the blend against explosive decomposition, of a normally liquid terpene hydrocarbon composition of which at least 80% by Weight consists of at least one bicyclic terpene =hydro carbon including at least 60% by weight of alpha-pinene.

It has been found that the terpene hydrocarbon compositions of the above-defined character, particularly the turpentines, are particularly effective to stabilize blends of tetraethyl lead with ethylene dichloride as the sole scavenger against thermal decomposition, particularly explosive decomposition, at temperatures above 100 C. Such terpene hydrocarbon compositions blend readily with the tetraethyl lead-ethylene dichloride blends, are normally liquid and are easily handled, and, particularly in the case of the turpentines are low cost materials which are readily available commercially.

The normally liquid terpene hydrocarbon compositions may consist of pure alpha-pinene, but more usual-1y will be mixtures of terpene hydrocarbons which consist essentially of about to about 98% by weight of bicyclic terpene hydrocarbons, including about 60% to about by weight of alpha-pinene (i.e., the alpha-pinene is one of the bicyclic terpene hydrocarbons and constitutes about 60% to about 90% by weight of the mixture of terpene hydrocarbons), and the rest are monocyclic terpene hydrooarbons, e.g., commercial alpha-pinene which contains :a small amount, less than 10%, of other terpene hydrocarbons, and the turpentines. Preferred mixtures of terpene hydrocarbons are the various turpentines which are wellknown articles of commerce and are more particularly described by W. D. Stonecipher in Kirk-Othmer, Encyclopedia of Chemical Technology, vol. 14, pp. 381-397, Interscience Encyclopedia Inc., 1955. Representative stabilizing turpentines are described in the following table, in which the proportions given are in percent by weight.

TERPENE HYDROOARBON MIXTURES SUITABLE FOR STABILIZING TETRAETHYL LEAD-ETHYLENE DIOHLO- RIDE BLENDS In addition to the above types, there may also be used destructively-distilled wood turpentine obtained by tractional distillation of the natural oil distillate formed during the destructive distillation of pine wood.

These turpentines normally show ASTM distillation characteristics such that the initial boiling point is at least about 152 C., the 5% point at least 156 C., the 50% point in the range 157 to 166 C., the 90% point at least C., and the 97% point not above about C., i.e., the preferred turpentines boil in the range of from about 152 C. to about 180 C.

The terpene hydrocarbon compositions will be employed in a small amount sufficient to stabilize the blend against thermal decomposition, preferably against explosive decomposition. Broadly, they will be employed in the proportion of from about 0.33% to about 6% by weight of the blend, more usually in the range of from about 0.67% to about 6% and, most preferably, from about 1% to about 1.5% by weight.

The tetraethyl lead-ethylene dichloride blend will contain from about 1 to about 2 theories of ethylene dichloride, i.e., from about 1 to about 2 moles of ethylene di- BLENDS FORMULATED ACCORDING TO THIS INVENTION Ingredients A B Percent by Percent by weight weight Tetraethyl lead 61. 48 61. 48

Ethylene dichloride--. 1 28. 21 2 31. 97 Du Pont Oil Orange 0.062 0.062

Turpentine 1.00 l. 2,6-di-tert-butyl-p-eresol 0. 016 0. 016 Kerosene 9. 232 5. 472

1 Corresponds to 1.5 theories. 2 Corresponds to 1.7 theories.

Such blends depend for thermal stability at elevated temperatures (100 C.-170 C.) on the presence of the terpene hydrocarbon mixture, turpentine. Neither the phenolic antioxidant nor the diluent kerosene (consisting essentially of saturated hydrocarbons) suffice in themselves to impart a significant degree of stabilization to the blends.

ternal temperatures. The bomb and its contents, under air or other atmosphere, is heated from room temperature to 150 C. at a steady rate over a period of 1.5-1.6 hours. Samples, surviving this heat-up period, are then held at 150 C. for a designated period as tabulated below or until explosion occurs. Results are expressed below in one or more terms of whether or not explosion occurred, the vapor temperature of the charge at the time that the explosion occurred, the amount of solid residue produced from the original liquid sample, and the percent of the tetra-ethyl lead that survived the treatment.

A variety of tetraethyl lead-ethylene dihalide blends, with and without stabilizer as identified below, were subjected to the 150 C. Static Bomb Test, either under an atmosphere of nitrogen (A) or air (B), with the results shown in the following tables. In such tables, EDC means ethylene dichloride, EDB means ethylene dibromide, and the numbers preceding EDC and EDB are the number of theories thereof. The stabilizers employed were (I) commercial steam-distilled wood turpentine, understood to contain about -80% by weight of alphapinene, up to about 2% by weight of beta-pinene, about 4-8% by weight of camphene, and about 15-20% by weight of higher boiling monocyclic terpenes;

(II) commercial sulfate wood turpentine indicated to contain about 60-65% by weight of alpha-pinene, about 25-35% by weight of beta-pinene, and about 58% by weight of high-boilers; and

(111) commercial alpha-pinene indicated to consist of about 98% by weight of bicyclic terpenes (about 91% a-pinene, 6% camphene, and 1% ot-fenchene) with the remainder being tricyclene and trace amounts of other monocyclic terpene hydrocarbons.

TABLE 1A.THERMAL STABiIlQIgY OF TEL-E'IHYLENE DIHALIDE BLENDS AT 150 C UNDER N2 ATMOSPHERE Turpentine Hours Vapor Solid Percent Test Blend (I), percent Explosion Time at Temp. at Residue, TEL

by wt. of 150 C. Exp]. gms. Surviving blend (1) TEL+1.5 EDC 0 (2) TEL+L0 EDC+0.5 EDB 13. 5 (3) TEL+0.5 EDB 2 Examples The stabilizing effect of the terpene hydrocarbons of this invention is illustrated hereinafter by means of the 150 C. Static Bomb Test, employing the following test procedure: 50 ml. of the test sample is placed in a stainless steel (or titanium-lined) bomb equipped with an 8000 psi. rupture disc and thermocouples for measuring in- The Table 1A data show (a) the blend (Test 1) containing ethylene dichloride (EDC) as sole scavenger is less stable (exploding during the heat-up period) than blends containing ethylene dibromide (EDB) (Tests 2 and 3), (b) turpentine, at 0.33% and 0.67% by weight of the blend, exerts a significant stabilizing efiect, (c) the TEL-EDC-turpentine blend of Test 6 is definitely more stable under the test conditions than the conventional Motor Mix formulation represented by Test 2.

TABLE 1B.STABILIZING TEL+L5 EDC BLENDS AT 150 C. UNDER AIR *The blend also contained 0.05% by weight of oil-soluble orange dye and 0.025% by Weight of 2,6-di-tertiary butyl para'cresol.

Table 1B shows that the turpentines and alpha-pinene are highly effective stabilizers, particularly at concentrations of at least about 1% by Weight of the TEL-EDC blend. The control (Test 1) containing ethylene dichloride as the sole scavenger decomposed explosively during the heat-up period. The effect of air versus nitrogen as the atmosphere is to mitigate somewhat the violence of the explosion when it occurs. Otherwise, the results obtained in both systems (Tables 1A and 1B) are roughly comparable. From Test 9, it appears that the phenolic antioxidant (2,6-di-tertiary butyl para-cresol) tends to sensitize the system towards decomposition, which can be overcome by increasing the concentration of the stabilizer to about 1%.

It will be understood that the foregoing examples have been given for illustrative purposes solely and that this invention is not restricted to the specific embodiments described therein. On the other hand, it will be readily apparent to those skilled in the art that, subject to the limitations set forth in the general description, variations can be made in the materials, proportions, and techniques employed without departing from the spirit or scope of this invention.

From the foregoing description, it will be apparent that by this invention antiknock blends of tetraethyl lead and ethylene dichloride are very efiectively stabilized against thermal decomposition and, particularly, against explosive decomposition, at temperatures above 100 C. In general, these stabilizers are low cost materials and are readily available commercially, whereby the stabilization is obtained economically. Accordingly, it will be apparent that this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An antiknock blend which consists essentially of (A) tetraethyl lead,

(B) about 1 to about 2 theories, based on the lead, of

a lead scavenger which consists of ethylene dichloride, and

(C) about 0.67% to about 1% by weight, based on the blend, of a turpentine which consists essentially of about to about 80% by weight of alpha-pinene and about 35% to about 2% by weight of betapinene, the rest being monocyclic terpene hydrocarbons.

2. An antiknock blend which consists essentially of (A) tetraethyl lead,

(B) about 1 to about 2 theories, based on the lead of a lead scavenger which consists of ethylene dichloride, and

(C) about 0.67% to about 1% by weight, based on the blend, of a turpentine which consists essentially of about to about by weight of alpha-pinene, up to about 2% by weight of beta-pinene, about 4% to about 8% by weight of camphene, and about 15% to about 20% by weight of higher boiling monocyclic terpenes.

3. An antiknock blend which consists essentially of (A) tetraethyl lead,

(B) about 1 to about 2 theories, based on the lead,

of a lead scavenger which consists of ethylene dichloride, and

(C) about 0.67% to about 1% by weight, based on the blend, of a turpentine which consists essentially of about 60% to about 65% by weight of alphapinene, about 25% to about 35% by weight of betapinene, and about 5% to about 8% by weight of high-boilers.

FOREIGN PATENTS 718,567 11/1954 Great Britain.

TOBIAS E. LEVOW, Primary Examiner.

E. C. BARTLETT, H. M. S. SNEED,

Assistant Examiners. 

1. AN ANTIKNOCK BLEND WHICH CONSISTS ESSENTIALLY OF (A) TETRAETHYL LEAD, (B) ABOUT 1 TO ABOUT 2 THEORIES, BASED ON THE LEAD, OF A LEAD SCAVENGER WHICH CONSISTS OF ETHYLENE DICHLORIDE, AND (2) ABOUT 0.67% TO ABOUT 1% BY WEIGHT, BASED ON THE BLEND, OF A TURPENTINE WHICH CONSISTS ESSENTIALLY OF ABOUT 60% TO ABOUT 80% BY WEIGHT OF ALPHA-PINENE AND ABOUT 35% TO ABOUT 2% BY WEIGHT OF BETAPINENE, THE REST BEING MONOCYCLIC TERPENE HYDROCARBONS. 